JPS61149833A - Fourier transform infrared spectrophotometer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to means for adjusting the position of an infrared photodetector in a Fourier transform infrared spectrophotometer.

- Conventional technology Spectrophotometers in the infrared and far-infrared regions use Ge or As2583 W, which is opaque in the visible light region, for the window material of the infrared light detector. For this reason, the light-receiving surface of the detector cannot be directly observed, making it extremely difficult to adjust the position of the detector. In particular, in the case of a detector using a crystal such as MCT or N8N, which is used while being cooled with a refrigerant such as liquid He or liquid nitrogen, it is installed and removed when not in use, so each time it is used, the Adjustments had to be made, which was a huge burden on the user.

C. Problems to be solved by the invention By automating the position adjustment of the photodetector, the difficulty of manually aligning the photodetector of a Fourier transform spectrophotometer in the infrared region can be solved. It is something.

2.Means to solve the problem X the photodetector in a plane perpendicular to the optical axis of the interferometer.

A driving means for moving in the y2 direction is provided, the interferogram is measured, and the position of the photodetector where the difference between the maximum value and the minimum value of the interferogram becomes the maximum is automatically searched.

5-action Fourier transform spectrophotometer measures an interferogram that represents the intensity change of the interferometer output light when the movable mirror of the interferometer is moved, with the amount of movement of the movable mirror as the abscissa; The method obtains the original spectrum of light by Fourier transform.If the center of the light receiving surface of the photodetector is shifted from the optical axis of the interferometer, the shape of the interferogram will be f, so Fourier transform However, if the photodetector's light-receiving surface is off the optical axis, the difference between the maximum and minimum values of the interferogram will increase. The present invention makes use of this fact, searches for the direction in which this difference increases, moves the photodetector in that direction, detects the position where the difference is maximum, and then the photodetector The center of the light-receiving surface of the interferometer coincides with the optical axis of the interferometer.

Embodiment FIG. 1 shows an embodiment of the present invention. 1 is a fixed mirror, 2 is a movable mirror, 3 is a beam splitter, and these constitute a Michael interferometer.
is a photodetector that can be attached to stage 6, which is movable in the three axes of X, Y, and Z.
M7 is a pulse motor that moves the stage in the X direction, M7 is a pulse motor that also moves the stage in the Y direction, and Mz is a pulse motor that moves the stage in two directions. 7 is a control circuit using a microcomputer. The control circuit 7 reads the output of the photodetector 5 and stores it in the memory 8, and also controls the motor M.
Control pulses are sent to x, My, and Mz to drive them.

The operation of the control circuit 7 when adjusting the position of the photodetector 5 will be briefly described. First, an interferogram is measured and the data is stored in the memory 8. Next, a pulse is sent to Mx to move the stage 6 one step in the positive direction of X, and the interferogram is measured again. Then, after normalizing the data with the maximum value as 1, the difference Δ between the maximum and minimum of the previous and current interferograms is compared, and if Δ is larger in the latter one, the stage is further driven in the same direction by steps. However, if Δ is smaller in the latter case, drive the stage two steps in the opposite direction and measure the second inter-7 erodulum. Determine 0 In this way, the position of the photodetector 5 in the X direction is determined at the point where Δ becomes maximum. Below Y direction 2
The position and direction are determined in the same manner.

Figure 2 shows how the shape of the interferogram changes depending on the center position of the photodetector.
indicates the position of the center of the photodetector in coordinates with the optical axis of the interferometer as the origin, and the interferograms shown in Figure 2B correspond to the four positions 1, 2, 3, and 4. It can be seen that the shape changes like 1 to 4, and the difference Δ between the maximum value and the minimum value becomes smaller as the photodetector moves away from the optical axis.

FIG. 3 is a flow chart of the X-direction position adjustment operation of the photodetector of the control circuit 7, and the operations in other directions are the same. First, drive direction register (provided in memory 8)
Set the +
Since it is in the X direction, drive the motor Mx in the positive direction for one pulse (d), measure the interferogram, and calculate Δ2.
, P is determined to be positive or negative (g), and if it is positive, that is, Δ2>Δ1, the operation returns to step 2), and the motor Mx is further driven in the specified direction (in this case, +X direction), and if the determination in (g) is negative, In this case, change the drive direction register setting to -X,
It is determined whether the level of Δ2 is greater than the level at which Δ2 is formed.
...and drives the motor Mx in the -X direction. If the judgment of (su) is YB2, Δ1. Assuming that Δ2 has reached the maximum value, the position adjustment of the photodetector 5 in the X direction is completed. The determination that Δ has reached the maximum can be made not only in step (S) above, but also in changing the driving direction after driving in the same direction multiple times (two times is possible). It is also possible to determine whether or not.

Effects According to the present invention, the position adjustment of the photodetector is automatically performed regardless of the acquisition, which greatly reduces the burden on the user in operating the device. In the case of a Fourier transform spectrophotometer, the shape of the reproduced spectrum changes more than the sensitivity due to the difference in the position of the photodetector, so it is important to ensure that the photodetector is always in the correct position. By setting the value to , correct spectrum measurement will be performed.

[Brief explanation of the drawing]

Fig. 1 is a plan view and block diagram of an embodiment of the device of the present invention, Fig. 2 is a graph showing the relationship between the position of the photodetector and the shape of the interferogram, and Fig. A shows the position of the photodetector. B shows the interferogram. FIG. 3 is a flowchart of the position adjustment operation of the photodetector in the above embodiment.

Claims (1)

[Claims] The photodetector is made movable in two axes in a plane perpendicular to the optical axis of the interferometer, and driving means for these two axes is provided, and the interferogram is measured to determine the difference between its maximum and minimum values. A Fourier transform infrared spectrophotometer, characterized in that a photodetector position adjusting means is provided for driving the driving means in a direction in which a maximum value of .